Structural elucidation of a tadalafil analogue found as an adulterant of a herbal product.

Food Addit Contam. 2006 May;23(5):446-51.
Zou P, Hou P, Low MY, Koh HL.

Department of Pharmacy, Faculty of Science, National University of Singapore, Science Drive 4, Singapore 117543.

A tadalafil analogue and hydroxyhomosildenafil were isolated from a herbal product marketed for erectile dysfunction. The structure of the tadalafil analogue was elucidated using LC-UV, high resolution MS, ESI-MS/MS, IR, and NMR. The compound was determined to be (6R,12aR)-2-amino-6-(1,3-benzodioxol-5-yl)-2,3,6,7,12,12a-hexahydropyrazino[1',2':1,6] pyrido[3,4-b]indole-1,4-dione. This compound should be included as a target compound when screening for adulterants in herbal products. This is the first published paper on a tadalafil analogue and hydroxyhomosildenafil found as adulterants of a herbal product.

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